Optimal design of hybrid optical digital imaging systems

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Abstract

Several types of pupil modulation have been reported to decrease the aberration variance
of the modulation-transfer-function (MTF) in aberration-tolerant hybrid optical-digital
imaging systems. It is common to enforce restorability constraints on the MTF, requiring
trade of aberration-tolerance and noise-gain. In this thesis, instead of optimising specific
MTF characteristics, the expected imaging-error of the joint design is minimised directly.
This method is used to compare commonly used phase-modulation functions. The
analysis shows how optimal imaging performance is obtained using moderate phasemodulation,
and more importantly, it shows the relative merits of different functions. It is
shown that the technique is readily integrable with off-the-shelf optical design software,
which is demonstrated with the optimisation of a wide-angle reflective system with
significant off-axis aberrations. The imaging error can also be minimised for amplitudeonly
masks. It is shown that phase aberrations in an imaging system can be mitigated
using binary amplitude masks. This offers a low-cost, transmission-mode alternative
to phase correction as used in active and adaptive optics. More efficient masks can be
obtained by the optimisation of the imaging fidelity.